If the light green coloration is in the new growth then it is completely normal. As the new leaves mature they will become darker green. The tree's growth is faster then is the allocation of nitrogen to them. Know that a grapefruit grown from seed as a container plant, will probably never fruit if kept in a container it's entire life. You might want to grow a Key Lime from seed which should bloom and fruit in 2 - 3 years, or a Mandarin which can fruit in 4-5 years if grown properly.

My tree was grown from a seed in 1984. It has been in a pot the entire time. For the first time it produced full size fruit. The leaves do vary in color from light green to dark.

I too have a young tree started from a seed. Not quite sure if it is grapefruit or lemon. I got fruit from the store and planted the seed. If there is only one tree, do they ever flower or produce fruit. Mine is about 6-7 years old and 4 ' tall. I have trimmed it up in the past to keep it from gettingso tall and lankey. Any information is really appreciated. Kari

I also have a grapefruit tree that one of my children grew from seed when he was a small boy. He is now 16 years old! It is in a pot, and is a beautiful little tree. The guy at the nursery I frequent told me it will probably never bear fruit. It is not because it is in a pot, my orange and lemon trees in pots bear fruit. I thought maybe it had something to do with hybridization. It is also the favorite larval food of all my citrus trees for the Swallowtail butterflies, so I will keep it!

Again, my tree which was grown from a seed is almost 24 years old. It has only flowered for the last 2 years. This year is the first time that fruit appeared. I did this in Pennsylvania.
The fruit was pretty good (flowered in April and fruit picked in November). The tree is about 10' tall and is in a 24" pot. Good luck.